Dresser compensating mechanism for grinding machines



ct. 30, 1945. a A. F. MARKUS DRESSER COMPENSATING MECHANISM FOR GRINDING MACHINES Filed Aug. 28, 1944 4 `Sheets-Sheet 1 v 4 NVE; N-r o Q -J Mugusz /7 War/KMS @a I l /W l /WZU GQTT'op- YJ Oct. 30, 1945.. A. F. MARKUS 2,388,066

DRESSER COMPENSATING MECHANISM FOR GRINDI-NG MACHINES Filed Aug. 28, 1944 4 Sheets-Sheet? 6 6 0 l 8 8 m .2N I `"n C A M G N I D N I R G R O F M s I N A H C E M G N I T A s N E P M O C R E S D` E R D Oct. `30, 1945; A. F. MARKUS 4 sheetssheet s N v e. N-ro 1=.- Waff/has ffy/MMM Uff.

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naso, 1945. A, MARKUS 2,388,066

DRESSR COMPENSATING MECHANISM FOR GRINDING MACHINES T'ro nan-'rvu I Patented Oct. 3 0, 1945 DRESSER COMPENSATING MECHANISM FOR GRINDING MACHINES August F. Markus, Detroit, Mich., assignor to Ex- Cell-O Corporation, Detroit, Mich., a corporation of Michigan Application August 28, 1944, Serial No. 551,478

`16 Claims.

1 The present invention is intended for application to grinding machines such, for example, as thread grinders, and has particular reference to grinding xmachines incorporating that general class of` mechanisms known as automatic dressing rcompensators which serve to modify automatically the relative displacement of grinding wheel and work by an amount requisite to compensate for the diminishment in wheel size necessarily incident to each dressing or truing of the same. AOne `objectof thepresent. invention is to provide in a grinding machine a mechanism of the general typerindicated embodying a novel arrangement for automatically rocking the grinding wheel Iand dresser as a unit generally transaxially of the work through ardistance proportional to adjustments in position of the dresser relative to the wheel.` i l Morespecically, it is an object to provide in a grinding machine such a mechanism in which the work and dresser are disposed for contact with the grinding' wheel at substantially diametrically opposite points on the latter, with the dresser pivoted on the wheel support for adjustment with reference to thewheel, and the wheel support itself arranged to be rockedautomatically relative to the work proportionally to adjustment of the dresser'. thus carrying both the wheel and f dresser with it `so that in` each adjustment `of dresseiyposition, the wheel is compensatingly ad- ,iusted in position relative to the work? `but without distributing the concurrently established new positional relation of the wheel and dresser.

, Another object is to provide in a grindingmachinea novel and simplified mechanism of the generaltype indicated adapted to use threaded sections of opposite lead of an adjusting screw or screws for respectivelyvarying the displace mentof the dresser with reference to the grinding `wheel and compensatingly effecting a relative shift of wheel and work.

Still another object is to provide in a thread grinding machine or the like an arrangement for adjustment of the helix angle r longitudinal position of the thread to be cut,` as well as its` size,` all coordinated in a `novel. manner with an automatic dresser compensator adjustment arrangement so as to render all of such adjustments available` and eiiective but without `interference with each other.

Further objects andadvantages of the invention will become apparent as the following description proceeds taken in connection with the accompanying drawings, in which:

Figure 1 is a front elevation of a thread grinding machine embodying the present invention.

` Fig. 2 is an enlarged right-hand end elevation of the upper portion of the machine of Fig. 1 with the work supporting mechanism shown partially in transverse section substantially along the `line 2-2 of Fig. 1.

Fig. 3 is a longitudinal sectional view through the work supporting mechanism, the same being taken substantially along the line 3--3 in Fig.. 2.

Fig. 4 is a View similar to Fig. 2, but with the `wheel and work supports, as well as the dresser support, shown `as sectioned substantially along the line 4 4" in Fig. 1.

Fig. 5 is a fragmentary detail perspective view of the mounting pad arrangement for the wheel supporting bracket.

Referring more particularly to the drawings of the exemplary embodiment of the invention here-` in disclosed, the same has been illustratedas in-v corporated in the thread grinding machine shown in Fig. 1. Such machine comprises a 'base I0 on the top of which is a work support, designated i generally as Il, and including centers I2` andM between which a workpiece (indicated at W in Fig. 3) is received and presented to a grinding wheel l5 which `is revolvable about an axis generally paralieling that of the work. The particulars of the specific form of work support illustrated constitute no part of the present invention, this work support being of substantially the form disclosed in a grinding machine covered by my copending application Serial No. 542,719. filed June 29, 1944. It will, accordingly, be sufficient for the moment to note simply that the work support here shown is such as to effect rotation of the work :and a timed reciprocation of the same to and fro past y shapen by Wear, a dresser mechanism is provided (see Fig. 2). This dresser mechanism may include one or morey diamond dresser points I6 carried by a dresser slide l1 and arranged to contact the grinding wheel l5 in an area on the latter substantially diametrically opposite that at which the wheel contacts the work. The

dresser slide I1 is mounted on a dresser supporting frame I8, movement of the latter being utilized in shifting the dresser step by step 'toward the grinding wheel for removing successive -inproportionality between crements of the latters periphery. The dresser mechanism per se may take any desired specic form, such, for exampley as that disclosed inthe G. Stewart Patent No. 2,311,263, issued February 16, 1943, the same normally embodying some drive arrangement for causing the dresser point or points to execute a predetermined motion with reference to the wheel periphery and in which the point moves from a retracted position into contact with the wheel, and after truing'the latter, back to its starting position. Positioning of the frame I8 determines the mean location (with reference to the grinding wheel) of the path of movement for the dresser point or points, and hence the depth of material dressed from the Wheel.

Each dressing or truing of the grinding wheel diminishes the latters diameter and the present invention is primarily concerned with a novel arrangement which compensates automatically for each such reduction in wheel size. In brief. the preferred arrangement shown (see Figs. 2 and 4) is such that a support I9 for the grinding wheel I5 is pivoted at 20 for rocking of the y wheel generally ,transaxially of the work W so thatthe wheell can be rocked about this pivot toward the Work through a distance such as to retain the active portion of the wheel in a iixed locus relative to the machine base I0. or in other Words, with reference to the grinding position for the workpiece. On the other hand, the dresser supporting frame I8 serves to move the dresser with reference to the wheel, and is for that purpose pivoted at 2I on the wheel support I9 itself so that when the latter is rocked, the wheel and dresser both move bodily as a unit with thetresult that their relative location is undisturbed by the compensating positioning of the wheel with reference to the work. Moreover, the respective supports I9 and I8 for both the wheel and dresser are rock simultaneously andA by a single adjustment device which retains accurate their movements.

As to the details of the particular Wheel support and dresser supporting frame shown, it will be observed that the wheel support I9 comprises a generally L-shaped casting of bell crank form, including a bifurcated upright arm I9a (Fig. 4) in which the grinding wheel I5 is journaled. At the juncture of the two arms of the bell crank, the Wheel support is pivoted by the pin 20 on a bracket 22 to which the wheel drive motor 23 is also fixed, the latter being belted to the grinding wheel. A compression spring 24 interposed between the horizontally projecting arm of the wheel support I9 and the underlying horizontal integral web 22a of the bracket 22 urges the wheel support I9 to turn about its pivot 20 in a direction to -shift the grinding wheel I5 toward the work (counterclockwise as viewed in Figs. 2 and 4). Such movement is limited by an abutment or stop pin 25 keyed at 26 to slide endwise within a bushing 21 fixed to the wheel supportV ment being adjustable endwise to determine the location of the wheel in a manner which will appear below.

The dresser supporting frame I 8 is, on the other hand, pivoted by the pin 2I 'on the outer end of the horizontal arm of the wheel support I9 rather than on the base. This frame I8 is urged to swing in a direction such as to move the dresser point I6 inward toward the grinding wheel I5 by a compression spring 28. The latter spring encircles'a pin 29 passing through an aperture 30 anchored at its inner end t0 in the frame I8 and I9, such abut-1 a. block 3| lixed to the wheel support i9, the .spring being interposed between a nut 32 on the pin 29 and an opposed face on the frame. Such movement of the dresser supporting frame I8 toward the lwheel support I9 is limited by a second abutment or stop 33 keyed as indicated at 34 for endwise sliding movement within a bore 35 in the block 3I yfixed to the wheel support.

Upon reference to Fig. 4, it will be seen that when utilizing a grinding wheel I5 of the particular diameter there shown, the points of contact PI and P2 for the work and dressing points respectively, as well as the center C of the grinding wheel, all lie in a common horizontal plane indicated by the dot-dash line L-L. Changes in the diameter of either the workpiece or wheel will alter this relationship somewhat, but the relation of the parts is such that when operating on any particular workpiece the changes in wheel diameter incident to dressing result in only anegligible change in vertical position of the wheel center C with respect to its initially established position with reference to the plane of the contact points PI, P2. Such minimization in the component of vertical movement of the wheel as compared to its lateral component of movement upon rocking of the wheel support, is accomplished by making the radius between the wheel support pivot 20 and the wheel center C long. It is also to be noted that the radius between the pivot point 2I for the dresser supporting frame I8 to the dresser point I6 is of substantially the same length as that for bodily swinging of the wheel so that there is no material change in the vertical position of the contact point P2 as the wheel diameter is reduced slightly by successive dressings.

Simultaneous and proportionate positional adjustment of the abutments 25, 33 is accomplished by an adjusting mechanism designated generally as 35. The latter includes a nut 31 in which are threaded a pair of screws 38. 39 having right and left-hand threads respectively. Such screws are rigid with respective ones of the abutments 25, 33 and are thus restrained against rotation by the latters keys 26 and 34. Turning the nut 31 in one direction causes the screws 38. 39 to draw the abutments 25, 33 inward. Recession of these abutments permits the dresser point I6l to be rocked toward the grinding wheel I5 and the wheel support I9 to rock toward the work W under the urging of the respective springs "28 and 24. Turning of the nut 31 in the opposite direction. on the other hand, projects the abutments 25. 33 outward, thereby causing the dresser' point I6 to retreat from the wheel and the wheel support I9 to swing away from the work. In the present instance, the abutments 25.Y 33 always move simultaneously and in opposite directions through precisely equal distances so that the res' sultant shift in wheel position exactly compensates for changes in wheel diameter incident to movement of the dresser point with reference 'I'he adjusting nut 31 may be turned manually or, if desired, by power in an automatic dressing cycle. For -manual operation, a hand wheel 40 is provided integrally with a is` in turn, integral with the nut 31. operation the ratchet wheel 4| by a pawl' 42 carried Aby plunger 43 reciprocable in' a transverse bore 44 in the wheel support I9. An adjustable guard 45, adapted to be locked in selected position on the wheel support I9 bya thumb nut 46, overlies a selectively variable portion of the series of ratchet teeth presented to For power ratchet wheel 4I whichv may be operated the thread being e e wheel I5 longitudinally` of theworla provision is the pawl, thus determining the angular distance of `turning movement imparted to the nut 31 upon each stroke `of the pawl.` Any'suitable means may be `employed for actuating the plunger 43in timed relationwith the remainder of the machine cycle, such, for example, as the hydraulic arrangement detailed `in the Ira JQSnader Patent llo.`

21,251,961, issued August 12, 194i. as disclosed inltthelatter patent, provision `may be made for initiatingsuccessive cycles of the dresser mechanism upon the completion of predetermined strokgrindingtmachine disclosed embodies a simple,

`rugged and yet highly precise mechanism for compensating for; the changes in wheel diameter incident to dressing it. In setting up the machine initially for a particular workpiece, the dresser control wheel 40 is revolved to locate the wheel support I9, with its grinding wheel I5, in a desired starting position and the -workpiece is 'advanced by the work support I I into contact with the wheel. Thereafter, the work is revolved and reciprocated to andfro past the wheel with an incremental or step-by-,step infeed of the work toward ,the wheel after each pass until a thread of predetermined depth is ground in the work` such"` depth,V being determined by limitingthe ad- Vance of thework toward the wheel. At `such points in this cycle o f operation as may be desired,

or at the end of .each such` complete grinding cycle, the work support II is caused to withdraw the workfrom contact with the wheel and the dresser mechanism is caused `to execute its predetermined cycle of movement to contact the wheel periphery with the dresser point or points I E and dress the Wheel. the dresser pointinto working position, thepawl 42 is actuated, therebyturning the nut 31 through a predeterminedincrement to withdraw the abutments 25,33` a. corresponding xed distance. Such` withdrawal ofthe abutments permits the spring. 218 `to advance the dresser incrementally toward the wheel preparatory to the next dressing operation and also permits the spring 24 to corn.l

pensatingly shift the wheel support and wheel with reference `to the work: to relocate thewheels periphery so that when the latter is trued by the relocated dresserpointthe wheel will contact the p work (upon `the next succeeding advance of the` latter` in grinding position) in precisely the position l previously occupied.

To accommodate changes in the helix angle of ground,` or relocation of the made for bodily shifting of the supporting bracket Since both the grinding wheel and dresser are supported from this same bracket 22, the two are shifted bodily and as a unit or selfcontained` 4assembly upon moving the bracket,

Y wherefore there is no disturbance of their relative locations. To accommodate such adjustable positioning of thebracket 22,` accurately machined surfaces 41, 48 are provided in opposed'relation on the machine base I and bracket 22, respectively." Such surfaces are located in parallelism withaplane normal to a'line passing through theaxes of the wheel and work, being vertical in this instance. A block` 4,9 see also Fig` `having flat, accurately machined, parallel opposite side faces is sandwiched between the surfaces" Upon Aeach advance of.

41, l48. This block is releasablysecured to the base I0 bvlbolts 5D having heads received in T- Slots 5I extending longitudinally of the surface 41the`block`49 being accuratelyguided for ad` justing movement axially of the workpiece li. c.; longitudinally of the surface 41) by a key 52. The bracket 22 is, in turngsimilarly secured to the block`49 by similarbolts having theirheads received in T-slots 53 Fig.` 5') `which are in this instance Aarcuate Adjusting `movementof the bracket on the, block is accurately guided by an arcuate key 54.` Thekey 54 and slots` 53 are centered" about a line passing through the axes of'the work and grinding wheel]` Both 4lateral and angular adjustment of the grinding wheel I5 can thus be accomplished readily and with precision.

As heretofore noted, the work support I I serves to rotate the work and translate it axially to and fro past the grinding Wheel I5 in timed relation to such work rotation, as well as to infeed and withdraw the work transaxially of the wheel. For such` purpose, the worksupport may take a variety of forms so long as itis of suchcharacter as to locaterthe work accurately with reference to the machine base when the work is in position to be ground. The latter requirement arises by reasonl of the fact thate'positioning of the work4 and wheel relative to each other is determined by fixing the locus of each with reference to the base. y

In the exemplary construction,r the `work support` II includes a main frame 55 (Figs. 2, 3 and 4l having an integral' upstanding headstockend plate 55 at one end and guideways 51 Ion the opposite end on which the adjustably clamped tailstcck 58 is received. Such frame 55 is slidable axially along apair of alincd guide barsk 59, 60 and is adapted tobe rocked or vpivotedabout such bars to carry the work toward and from the grinding wheel. A work supporting spindle 6I is journaled in the headstock'by antifriction bear-jy ings 62,` 63, the latter bearing being carried by a tubular extension B4 in a gear housing 65 remov-` ably iixed to the upright `55. e

Provision is made for translatingthe work support frame 55 in timed relationwith the` rotation `at the sideof a supporting lug 69 opposite the leg 61 to coact with thelatter in restraining the head againstmovement axially of the guide rod.

In the upper portion of the head frame 66. a sleeve t 10 is revolvably journaled and is open at its rightf hand end.V The tubular extensionu64 is telescoped within this open end of the sleeve so that the two frames 66 and 55 areslidably connected for tilting movement in unison while still permitting displacement of thefsame relative to each other in a direction axially of the guide rods 59, 60. `A feed nut 1I is` clamped to the outer end of the supporting sleeve 10 and threaded on a master feed screw I2 keyed to the spindle 5I. The nut 1I and its supporting sleeve I0 arenormally held stationary so that turningpf the feed screw 12 within the nut, incident to rotation of the spindle 6I, causes the latter to be fed axially in timed e relation with its rotation.

Rotation of the work spindlel and `its feed screw '|2 isl accomplished from a drive shaft I3 disposed concentrically with the axis of tilting or pivotal motion of the work support about the guiderods 59, 60 sovthat the drive connections will remain undisturbed during all tilting movement of the latter. This shaft 13 is journaled within the tubular shaft or guide rod 59 heretofore mentioned, and is driven by worm gear 14 fixed to its outer end and meshed with a worm 'l5 which is, in turn, connected by a pulley 16 and belt with an electric drive motor '|8 xed to the lower portion of the machine base |0. A pinion 19 xed ,to th'e'drive shaft '|3 meshes witha gear 80 carried bya shaft 8| journaled within the block 68. For the drive connection for revolving the spindle 6|, the shaft 8| has a sliding spline connection 82 with a shaft 83 journaled in the main frame 55 and carrying a gear `84. The latter gear meshes with a second gear 85 rigid with a sleeve 86 keyed to the spindle 6|. 4

Tilting motion is imparted to the work support frame 55. for moving the workpiece transaxially of the grinding `wheel by means of a size control mechanism designatedgenerallyas 81 (see Figs. 2 and 4). Such size control mechanism includes an axially movable nut 88 slidably guided and restrainedagainst rotation by the rearwardly projecting 'portion 89 of a bracket 90 xed to the frontof the machine base I0. Laterally projecting trunnions 9| on this nut are connected by pivoted links 92 with a pair of depending feet 93 rigid with an intermediate support or apron 94 (see also Fig. 3). The latter is also pivoted 'on the guide,bars 59, 60 although restrained against translation. The frame 55 rests directly on the intermediate support at all times in sliding engagementwith' it, apin 95 on the intermediate support being vdisposed to Acontact a bar 96 at# tachedfto the frame 55. A compression spring 91 vurgesftheframe counterclockwise to retain contact of the Ipin with the bar.' As the nut 88 is slid outward, the intermediate support 94 is tilted toward the grinding wheely |5,

carrying `the work support frame 55 and workpiece with it, whereas movement of the nut in the vopposite direction results in rocking the workpiece away from the grinding wheel.

The nut 88 may be moved endwise for shifting the Work either by rotation of a screw 98 threaded in the nut or by non-rotative bodily endwise shifting of such screw. Such bodily endwise shifting of the screw is used herein for moving the workpiece quickly into or out of the operating zone, and for that purpose a piston 99 rigid with the inner end of the screw is received in a hydraulic cylinder |00 stationarily fixed to the machine base I0. Upon admission of pressure fluid to the cylinder through the port |0| and exhaust of iiuid from the other port |02,'the piston 99'is moved to the right (as viewed in Fig. 4), thus tilting the work support frame 55 counterclockwise yto withdraw the workpiece quickly from "contact with the wheel, whereas admission of pressure fluid through the vport |02 and exhausting of fluid through vthe other port |0| causes the piston to move in the opposite direction to rock the work forward into juxtaposition with the wheel. The supplying and exhausting of pressure iiuid for this purpose may be accomplished through the use of suitable hydraulic mechanism, various forms of which are well-known in the art, and consequently not illustrated here.'

Rotation of the screw 98 while restraining it against endwise movement to move the nut 88, and thus the workpiece, is normally utilized in j incrementally advancing the work in the course of grinding as, for example, with one step of ad- Vance after each pass of the work past the grinding wheel. For that purpose, the screw 98 may be revolved manually by a size control wheel |03 splined to the same or, if desired, a suitable ratchet type drive mechanism maybe incorporated (not shown) inthe casing |04 totuinthe screw' 98 incrementally in timed relation with the reciprocation of the work support. A suitable ratchet type mechanismy for the purpose is disclosed in the GuentherfBrinkmann application Serial No. 435,224, led March 18, 1942, andassigned to Ex-Cell-O Corporation, assignee of the present application, but since the same consti-l tutes. per se, no part of the present invention it need not be illustrated in detail here.

Provision may also be made in the work support for other refinements of adjustment butI w 'ch again constitute, per se, no part of the present invention. For example, provision may be made for locking the bar 96 in selected positions of angular adjustment by a clamp |05 (Fig. 1) to condition the machine for grinding a thread of corresponding taper on the work. Any such adjustments being made entirely in the Work supporting side of the machine, however, do not interfere with, or alter one way or another, the dresser compensating arrangement disclosed.

I claim as my invention:l

1. In a grinding machine, the combination of a. base, a. rotatively driven grinding wheelV having a support, means pivoting said ysupportA on said base for bodily rocking of the same in adirection transaxialof said wheeL-work supporting means for presenting a workpieceto the periph-` ery of said Wheel, ,a dresser disposed for contact' cally opposite the point of wheel and work contact, and means pivotally supporting said dresse/1` on said wheel support for rocking motion of the dresserwith reference to said wheel transaxially of the latter, rocking of said wheel support servring to effect bodily movement of said wheel and dresser in unison with reference to the Work.

2. In a grinding machine, thecombination of a base, a rotatively driven grinding wheel having a support, means pivoting said support on said base for bodily rocking ofthe same in a direction transaxial of said wheel carried thereby, work supporting meansfor presenting a workpiece to the periphery of saidwheel, a dresser disposed for contact with said'wheel at a'point 'substantially diametrically opposite the point of wheel and work contact, means pivotally supporting said dresser on said Wheel support for rocking motion of the dresser with referenceto said wheel' transaxially of the latter, rockingv of said wheel support serving `to eiect bodily movement of said wheel and dresser in unison with reference to the work, spring means respectively urging said wheel support to swing said wheel toward the work and said dresser to swing toward said wheel, abutment means for limiting the movement of said wheel support and dresser by said spring means, and adjustment means for'altering the setting of said abutment means with reference to said' wheel support and dresser simultaneously.

3. In a grinding machine, the combination of a base, a rotatively driven grinding wheel, means including a support pivoted on said base mounting said wheel for bodily rocking motion in a direction transaxial of the wheel, a work support and a dresser support disposed to present respectively a workpiece and a dresser forcontact with the'periphery of said wheel at wheel, `first and n abutments.

`supporting means substantiallydiametrically opposite points, means pivotally mounting said i dresser support on said wheel support for movement of theformer generally transaxially of said i second bias springs acting rei fspectively to urge said wheel vsupport toward said work support and `said `dresser support toward said wheel, first and second abutments slidably mounted on saidwheel supportnd positioned respectivelyto limit the rocking of said wheel support and dresser support under the urging of theirfcorresponding springs, `two screws of right andileft-hand leadtconnectedto respective ones of said'abutments and restrainedagainst rotation, and a single adjusting nut threaded on both said screws and restrained against axial movement for revolving on said screws to adjust simultaneously and in equal amount the displacement of `said 4. In a grinding machine, the combination of `work and `wheel supports having means thereon for supporting respectively a `workpiece and a rotatively drivenngrinding wheel with the work i presented to the wheel, means pivotallymounting `said wheel support for rocking motion of the i same; in a direction` generally transversely of a workpiece `carried by said work support, a dresser,

instable `rocking motion generally transaxially of the grinding wheel carried by said wheel support,

and means for effecting simultaneous rocking motion `of saidwheel support and dresser supporting rotatively driven grinding wheel, means pivotaliy mounting said Wheel support for bodily rocking i of the same with the wheel carried thereby toward and from the work support, an adjustment device including a revolvably mounted member restrained against axial movementianda pair oi elements restrained against rotation and threadably connected to said member by respective right and left-hand sets of threads for axial movement of such elements in `respective opposite directions in response to rotational adjustment of said member, lmeans operable in response to axial movement of one of said elements for moving said dresser relative to said wheel transaxially of the latter, and means responsiveto axial movement of the other of said elements for rocking said wheel support. i l

pivoting said dresser for adv means about their respective `pivots and coordinated to alter the displacement of the wheel with reference to the work by an amount equal to the alteration in displacement of the dresser relative to the wheel.`

5. In a grinding machine; the combination of work and wheel supports having means thereon for `supporting respectively a workpiece. and a rotatively` driven grinding wheel withthe work presentedto the wheel and with the axes of the wheel and work generallyparallel to each other,

means pivotally mounting at "least one of said supports for rocking-motion of the same transverseiy of the work, a dresser, supporting means pivoting said dresser for adjustable rocking motion transaxially of the grinding wheel carried by said wheel support, and means for effectingv `rocking motion of said pivoted mounting means` of said dresser supportproportionate tomotion ing means.` i

6. In a grinding machine, thecombination of work and wheel supports having means thereon for supporting respectively a workpiece and a ro- 8. In a` grinding machine, the combination of work and wheel supports having means thereon for supporting` respectively a workpiece and a rotatively driven grinding wheel, means pivotaliy mounting said wheel support for bodily rocking` ofthe same with the wheel carried thereby toward and from the work support; a dresser and `a support` therefor` pivoted on said wheel support, an adjustment device including a member revolvably mountedon said wheel support restrained against axial movement and a pair oi elements threadably connected to said member by respective right and left-hand sets of threads `for axial movement of such elements in respective opposite directions in response to rotational adjustment lof said member, means operable in `response to :axial movement of one-of said elements for rocking said dresser support relative to said `wheel support in a direction to move said dresser transaxially Vof said wheel, and means responsive to axial movement of the other of said elements for `rocking said wheel support.`

9. In a grinding machine, the combination of work and wheel supports having means thereon for supporting respectively a workpiece and a l rotatively driven grinding wheel, a dresser, `a rotatively driven grinding wheel, a dresser, an adjustment device including a revolvably mounted member `restrained against axial movement and a pair ofelements restrained against rotation and threadably connected to said member. by respecn 1 tive right and left-hand sets of threads for axial movement of such elements in respective opposite directionsin response torrotational adjustment of said member, means operable in response to `axial movement of one of said elements forv movi ing said dresserrelative to said wheel transaxially lof the latter, and means responsive to axial movement of the other of saidelements for effecting relative movement between said supports generally transversely of the work and proportionately to movement of said dresser by said one element.

- 7. In a grinding machine, the combination of work vand wheel supports havingmeans thereon for supporting respectively a` workpiece and a tatablenut restrained against axial movement and having two screws with respective `right and left-hand threads threaded therein and restrained against rotation,V whereby rotation of said nut serves .toprojector retract said screws simultaneously with reference to the nut, means responsive to axial movement of one of said screws for moving said dresser relative to the wheel generally `transaxially of the latter, and means responsive to axial movement of the other of said screws for effecting relative movement between said supports generally transversely of the work and proportionately to the movement of said dresser by said one of said screws. n

10. In a grinding machine, the combination of work and wheel supports having means thereon for supporting respectively a workpiece and a ro- `tatively driven` grinding wheel, a dresser` carried `by a support pivotally mounted on said wheel support for rocking motion of the dresser with reference to said grinding wheel transaxially of the latter, means pivoting said wheel support for rocking of the vsame generally transversely of a workpiece carried by said work support,` and means for rocking said wheel support about its pivot in proportion to pivotal adjustment of said dresser in reference to the wheel.

11. In a grinding machine, the combination of a rotatively driven grinding wheel, a work support and a dresser support disposed to present respectively a workpiece and a dresser for contact with theeperiphery of said wheel at submean pivotally mounting stantially diametrically opposite points, a wheel support journaling said grinding wheel-for rotation and pivoted to rock the. latter bodily toi driven grinding wheel journaled thereon for roward and fromthe work presented by said work support, the axis of lsaid Vpivot paralleling the axis of wheel .rotation and being displaced from the latter suiciently far that thecomponent of movement of said Wheel ina direction normal l to a line passing throughsaid pointsof contact is small-asA compared to its component of movement in the `direction of. said line duringthe rocking of said wheel, means pivotallymounting said dresser -support on said :wheel support for rocking of the latter about an axis paralleling that of the pivot for said wheely support, and

means for coincidentally rocking said wheel 'and dresser supports inthe same directions about their respectivepivots through proportionate an'. gulardistances. l 1

152. In a grinding machine, the combination of a rotatively driven grinding wheel, a work support and a dresser supportdisposed to present :a base, a grinding wheel and comprising dresser assembly a bracket having pivoted Athereon a wheel support which. vin turn has a rotatively v tation about an axis paralleling the pivotal axis of said wheel support, and a dresser support pivoted on said wheel support for rocking` of a dresser tra-nsaxially of said Wheel, work supporting means' on Ysaid base for presenting a workpiece to the periphery of said wheel, means accurately guiding said assemblyin bodily adjusting movement thereof with reference to said base both in a rectilinear path paralleling the wheel axis and in an arcuate path centered about a line passing between the Wheel axis and the point of contact of said wheelwith the work, and means for releasably securing said assembly in selected .positionsof adjustment thereof.

respectively a ,workpiece and'a dresser for contactl with the periphery of said wheel at substantially.diametrically opposite points, a wheel f support journaling said grinding wheel forrotation and pivoted to rock the latter' bodily toward and from the work presented by said work support, the axis of said pivot .paralleling `the axis of wheel rotationand `being displaced from the latter sufliciently far that the component of a line passing saidpoints of contact-is'small as compared toits component of movement in the direction of said line during rocking of said wheel,` said dresser support on said wheel support for rocking of the latter about an axis: paralleling port and displaced from the point'of dresser contact with said wheel by a distance substantially equal to the distance between said wheel axis and the pivot axis of said wheel` support, vand means for coincidentally-rocking said wheel in dresser supports-in thefsame directions about theirrespective pivots through angulardistances constantly maintained equal. f

13. In a grinding machine, 'thecombination of a base, a grinding'wheel and dresser assembly comprising a bracket having pivoted thereon a wheel supportfwhich in turn has a rotatively driven grinding wheel journaled thereon for rotation about an axis paralleling the pivotal Vaxis of said wheel support and a dresser support pivoted on said wheel support for rocking of a dresser transaxially of said wheel, work supporting lmeans on said base for presenting a` work piece to the periphery of said wheel, said base and bracket presentingl opposed at mounting faces both paralleling a plane substantially normal to a line passing through the axis of wheel rotation and Athe point of wheel contact with the work, means interposed Ybetween said faces-for accurately guiding said assembly in bodily adjusting movement thereof with reference to the base both in a rectilinear path paralleling the wheel axis and an arcuate path centered about said line, and means for releasably clamping said asf sembly in selected positions of adjustment thereof.

.fmovement of said wheelvin a direction normal to .v

' means for not only vjournaled, means for 15. In a thread grinding machine having a base with a Work support thereon for electing timed rotation and axial reciprocation of a workpiece aswell as transaxial infeed and retraction of the workpiece, a grinding Wheel and dresser a rotatively driven grinding a Wheel support on which said wheel is pivoting said wheel support on said base about an axis paralleling that of wheel,

said Wheel for rocking of the latter generally transaxially of the work, a dresser support pivoted on'said wheel support for rocking of a dresser point thereon toward and from the peripheral portion of .said wheel opposite vthe work,l and swinging said dresser support about its pivot toward said wheel but for also simultaneously rocking said wheel support toward said work support through an angular disthat of said wheel suptance such as to displace said wheel bodily toward said work support by anamount precisely equal to the advance of said dresser point with reference to said wheel.

16. In a thread grinding machine having a base with a work support thereon adapted to ect timed rotation and axial reciprocation of a workpiece kas well as transaxial infeed and retraction of the workpiece, a grinding wheel and Y dresser assemblyy comp/rising` a rotatively driven l movement of such grinding wheel; a wheel support on which sa'id wheel is journaled, means for pivoting said wheel support on said base about ran axis paralleling that of said wheel for rocking of the latter generally transaxially'ofthe work, a dresser support pivoted on said wheel support for rocking of a dresser point thereon toward and from the of said wheel opposite the work, any adjustment device including a member revolvably mounted von said wheel support and yrestrained against axial movement as well as a pair of elements restrained against rotation and threadably connected to said member by respective right and left-hand sets of threadsfor axial elements in respective opposite directions in response to. rotational adjustment of said member, means operable in response to axial movement of one of said elements for rocking said dresser support about its pivot, and means responsive to axial movement of the other of said elements for rocking said wheel AUGUST F. MARKUS.

support about its pivot. 

